1. Field of the Invention
The present invention relates to a differential mode amplifier driving circuit capable of simplifying a circuit and reducing a loss generated in a passive device, by only applying an input signal to one input terminal of the differential mode amplifier, without using a balun.
2. Description of the Related Art
Generally, a differential mode is frequently used in an amplifier such as a low noise amplifier (LAN), a power amplifier (PA), or the like, in an IC chip for a millimeter-wave band signal transmitting and receiving system. When an amplifier is designed by using the differential mode, a virtual ground may be utilized and noise characteristics may be improved as compared with a single mode.
However, a separate balun circuit for converting a single mode signal into a differential mode signal is required, in order to combine a differential mode amplifier with other components operated in a single mode.
An additive circuit, such as a marchand balun circuit, a rat race circuit, or the like, is required in order to operate a differential mode circuit of the related art in a single mode, that is, through a single input. The marchand balun circuit uses the coupling of two ¼ wavelength transmission lines, while the rat race circuit also uses a ¾ wavelength long transmission line. These circuits occupy a large area within an IC chip, and may cause a large loss at a high frequency within a millimeter-wave band or a tera-hertz band.
According to the Related Art Documents, Patent Document 1 (US Patent Registration No. 7027792) discloses that a single radio frequency (RF) and a differential local oscillator (LO) are present at an input terminal, as a single balanced mixer. However, this constitution requires differential input at a local oscillator (LO) input terminal, and thus, a balun circuit is required at the LO input terminal in the case in which an output of an oscillator generating an LO signal is in a single mode. Patent Document 2 (Korean Patent Registration No. 2009-0104160) does not disclose that a differential mode amplifier is driven without a balun circuit.